Grass - Mowing

Mowing/Lawn Care

The most important cultural practice associated with maintaining any turfgrass is mowing. When part of the grass plants’ leaf system is removed by mowing, the plant reacts by using high amounts of carbohydrates to replace the leaves that were cut off. Only when the leaves are replaced does root and stem growth renew. The greater amount of leaf surface that is cut off at each mowing, the longer root and stem growth is reduced. Research formed that when no more than 1/3 of the leaf system is removed at one cutting, negative effect on root and stem growth is minimal. The cutting height has an effect on root size. There is a direct relationship between cutting height and the total volume of root system.

Grass clippings should be left on the turf. They do not contribute to thatch so there is no need to “bag” them if a reasonable mowing program is followed. Clippings should only be caught and moved to the compost pile when scalping prior to overseeding.

Edging and Trimming
Edge along walks and curbs as is needed. Monofilament trimmers can be used along steel edging, curbs, and other hard surfaces but never around trees or shrubs.

Scalping
Scalping involves the removal of the dead upper parts of the plant.

The reason scalped lawns “turn” green earlier is that the physical removal of all the brown leaf material allows more of the green leaves to be visible. Scalping a turf in the spring is not a part of any professional turf management program and should not be done on your turf, except prior to overseeding with winter grasses.

SUGGESTED MOWING HEIGHTS

Turfgrass Best Height Mow when lawn is

Bermudagrass1 ½ inch2 ¼ inches

Hybrid Bermudagrass1 inch1 ½ inch

Kentucky Bluegrass2 inches3 inches

Texas Bluegrass2 inches3 ½ inches

Buffalograss3 inches4 ½ inches

Centepedegrass 2 inches3 inches

Perennial Ryegrass2 inches3 inches

St. Augustine2 inches3 inches

Tall Fescue2 inches3 inches

Zoysiagrass 1 ½ inches2 ¼ inches

Weed Control
Weed control products are divided into two groups – those that kill weed seed as it germinates (pre-emergent herbicides) and those that control weeds after they are growing (post-emergent herbicides). The organic pre-emergent is corn gluten meal. The organic post emergent is vinegar.

Pre-Emergent Weed Control
Pre-emergent herbicides must be in place before the weed seed begins to grow. Annuals, like henbit and annual bluegrass that germinate in the fall as soon as the weather cools. There could be as much as a month or so difference in the arrival of the first significant cold front. For a pre-emergent to be effective for winter weed control in north Texas, it should be applied around September 15 or a month or so later in the southern part of the state.

The same holds for the spring. Many annual weeds, like grassburs and crabgrass, germinate in the early spring, again depending on temperatures. In northern Texas corn gluten meal should be applied by early March, even earlier farther south. Some years these dates may be too late. Success depends on changes in the weather. Early or late falls and early or late springs make pre-emergent programs difficult. Once in a while the program may fail. Corn gluten meal will fail as a pre-emergent if the soil and weed seed stay moist for a long period after treatment is applied. The constant moisture will override the herbicidal effect, the small roots will start to grow and the fertilizer value of the corn gluten meal will give you very large weeds. Just mow them.

Post-Emergent Weed ControllPost emergent control of weeds is done in the organic program primarily with vinegar and vinegar-based products. Spray during warm or hot weather. Straight vinegar (10 or 20%) can be used or vinegar-based products..

Mow a little higher than the organiphobes recommend. Start the season at 1 1/2" to 2" and raise to at least 3" by mid summer. Mow weekly or more often if necessary, leaving the clippings on the lawn. Put occasional excess clippings in the compost pile.

Do not send clippings to the dump.
Do not use line trimmers around trees.
Do not scalp the lawn in the spring. Scalping is hard on equipment, exposes the soil to sunlight and weed germination, and wastes organic matter.

QUESTION: Fire department officials and foresters are telling us to cut our lawns as short as possible to prevent the spread of wildfires. You have said that scalping a lawn is a bad idea. We have St. Augustine grass, and I leave it as long as my mower will allow to protect the roots. If I scalp the lawn, what effect will it have on the grass this spring? D.M., Plano

ANSWER: Scalping exposes the soil and leads to the growth of weeds on the bare areas. There would also be more risk of freeze damage if cold weather occurs. Rather than scalping, mow the lawn at one setting lower than usual and water it once a week to minimize the fire risk. Cities should recommend putting 61/2 inch of compost in planting beds and on turf areas. This would help reduce the fire hazard and feed the soil and plants.